1. Field
A bush bearing and a scroll compressor including a bush bearing are disclosed herein.
2. Background
A scroll compressor is a compressor in which a non-orbiting scroll is disposed in an internal space of a container, and an orbiting scroll orbits in engagement with the non-orbiting scroll to form a plurality of compression spaces, which include a suction chamber, an intermediate pressure chamber, and a discharge chamber, between a non-orbiting wrap of the non-orbiting scroll and an orbiting wrap of the orbiting scroll. The scroll compressor can obtain a relatively higher compression ratio than that of other kinds of compressors, and obtain a stable torque because a refrigerant may be smoothly suctioned, compressed, and discharged. Therefore, the scroll compressor is widely used for compression of refrigerant in, for example, an air conditioning apparatus.
Scroll compressors may be divided into a fixed radius type, in which an orbiting scroll always orbits on a same trajectory irrespective of a change in a compression condition, and a variable radius type, in which the orbiting scroll retreats in a radial direction according to the compression condition.
FIG. 1 is a vertical cross-sectional view of a related art scroll compressor. As illustrated in FIG. 1, the related art scroll compressor may include a container 1; a drive motor 2 that is disposed in an internal space of the container 1, and generates a rotating force; a main frame 3 fixedly disposed on the drive motor 2; a non-orbiting scroll 4 disposed at a top of the main frame 3; an orbiting scroll 5 disposed between the main frame 3 and the non-orbiting scroll 4, eccentrically coupled to a rotational shaft 23 of the drive motor 2, and forming a plurality of compression spaces P that continuously moves along with the non-orbiting scroll 4; and an Oldham ring 6 that is disposed between the non-orbiting scroll 4 and the orbiting scroll 5, and prevents a rotational movement of the orbiting scroll 5.
The main frame 3 may be welding-coupled to an inner circumferential surface of the container 1, and a shaft hole 31 may be formed at a center of the main frame 3 to pass through the main frame 3. A pocket groove 32 may be formed at an upper end of the shaft hole 31 so that a boss 53 of the orbiting scroll 5 may be orbitably inserted into the pocket groove 32.
A non-orbiting wrap 42 may be provided at a bottom of a plate 41 of the non-orbiting scroll 4, and a suction hole 43 may be formed at one side of the plate 41 of the non-orbiting scroll 4. A discharge hole 44 may be formed at a center of the non-orbiting scroll 4.
An orbiting wrap 52 may be provided at a top of a plate 51 of the orbiting scroll 5 so as to form the plurality of compression spaces P in engagement with the non-orbiting wrap 42 of the non-orbiting scroll 4, and the boss 53 may be provided at a bottom of the plate 51 of the orbiting scroll 5 so as to be coupled to the rotational shaft 23. A bush bearing 54, which is configured to be coupled to a pin 23d of the rotational shaft 23, may be inserted into an inner circumferential surface of the boss 53.
The rotational shaft 23 may include a shaft 23a press-fitted to a rotor 22 of the drive motor 2; a main bearing 23b and a sub bearing 23c, respectively, provided at both vertical ends of the shaft 23a and supported by the main frame 3 and a sub frame 7; and the pin 23d, which is eccentrically provided at an upper end of the main bearing 23b and coupled to the bush bearing 54 inserted into the boss 53 of the orbiting scroll 5. An eccentric mass 8 to counteract an eccentric load, which is caused by an orbiting motion of the orbiting scroll 5, may be coupled to the main bearing 23b or the shaft 23a. 
In the drawing, reference number 11 refers to a suction pipe, reference numeral 12 refers to a discharge pipe, and reference numeral 21 refers to a stator.
In the related art scroll compressor, when power is applied to the drive motor 2 to generate a rotating force, the orbiting scroll 5 may be orbited with respect to the non-orbiting scroll 4 by the rotational shaft 23 coupled to the rotor 22 of the drive motor 2 to form the plurality of compression spaces P, and thus, a refrigerant may be suctioned, compressed, and discharged. At this time, the orbiting scroll 5 may receive a centrifugal force generated by the orbiting motion, a gas force generated by compressing the refrigerant, and a gas repulsion generated in an opposite direction of the centrifugal force, and thus, a movement of the orbiting scroll 5 may be unstable. However, the orbiting scroll 5 may continuously orbit by being appropriately adjusted in a state of being supported by the main frame 3.
However, in the related art scroll compressor, a large height difference “Δh” occurs between a supporting point A at which the rotational shaft 23 is supported by the main frame 3, and an action point B at which the rotational shaft 23 acts on the orbiting scroll 5, and thus, a large eccentric load may be applied to the rotational shaft 23. For this reason, a bearing load caused by a gas force may increase, and thus, compression efficiency may be reduced due to friction loss. Moreover, an action force at a welding point based on the gas force may be high, and for this reason, noise of the compressor may increase, causing a reduction in reliability.
Moreover, as a large eccentric load may be applied to the rotational shaft 23, a weight of the eccentric mass 8 disposed at the rotational shaft 23 may need to be increased, and for this reason, the cost may increase. Also, a deformation amount of the rotational shaft 23 may increase, and for this reason, compression efficiency may be reduced due to friction loss. Also, a centrifugal force of the eccentric mass 8 may increase, and thus, an action force at a welding point may increase. For this reason, noise of the compressor may increase, causing a reduction in reliability.
Moreover, the shaft hole 31, in which the main frame 3 supports the rotational shaft 23, may be separated, by a certain interval, from the pocket groove 32, into which the boss 53 of the orbiting scroll 5 is orbitably inserted, and thus, a length of the main bearing 23b of the rotational shaft 23 may become longer. Also, a large eccentric load may be applied to the rotational shaft 23, and thus, a bearing length of the main frame 3 may increase. For this reason, an axial direction length of the compressor may increase, increasing material costs. In addition, there is a limitation in increasing a stacked height of a motor within a limited axial direction length of the compressor, and for this reason, there is a limitation in increasing a capacity of the compressor with respect to a length of the same compressor.